The United Kingdom is currently witnessing a rare 'painted lady summer,' an event that occurs approximately once every decade, bringing with it a significant increase in migratory butterflies. Wildlife charity Butterfly Conservation has initiated its annual Big Butterfly Count, encouraging the public to record sightings of these distinctive insects to aid in population assessments.
Warm weather conditions across Europe this spring are believed to have driven millions of painted lady butterflies to the UK. Reports indicate swarms of the butterflies have been observed feeding and mating, and a new generation is now emerging nationwide. This phenomenon is considered one of the longest insect migrations globally, spanning from sub-Saharan Africa to Europe and completed over successive generations.
The butterflies' journey begins with adults born in sub-Saharan Africa flying to north Africa to reproduce. Their offspring then migrate across the Mediterranean to southern Europe, where they mate and lay eggs. The generation that hatches in southern Europe makes the final journey to the UK in late spring. The current influx is composed of a new generation born from those that arrived in the UK.
Butterfly Conservation stated that this year is on track to be the third-best year on record for painted lady numbers, following 1996 and 2009. While the last 'painted lady summer' in 2019 saw over 420,000 recorded sightings, this year's numbers have already surpassed last year's total and are also higher than those recorded at the same point in 2019. This suggests the current event could potentially exceed the previous decade's peak.
"The inter-continental migration of painted lady butterflies is a wonder of the natural world and one of the longest insect journeys on the planet," said Professor Richard Fox, head of science at Butterfly Conservation. "The numbers we're seeing here at the moment have already dwarfed the total number of painted ladies we saw last year, and we're absolutely delighted."
The painted lady, characterized by its pinky-orange, black, and white patterned wings, is a popular species. The emerging generation is preparing for the next stage of their migration. The Big Butterfly Count provides an opportunity for the public to contribute to understanding this migration.
These butterflies feed on various flowers, including buddleia, and their caterpillars primarily consume thistles. Historically, abundant populations of painted ladies have aided in controlling invasive thistle species.
While the exact reasons for the UK experiencing these mass arrivals remain under investigation, Butterfly Conservation links them to successful breeding seasons in Africa and southern Europe. Fluctuations in insect populations are often attributed to factors such as food availability and predator numbers. This year's favorable weather conditions have particularly supported the butterflies' migration.
Kate Merry, head of engagement at Butterfly Conservation, described the event as an "astonishing" and "unexpected twist" for this year's Big Butterfly Count, highlighting the remarkable endurance of the seemingly delicate insect for such long-distance travel. "We've already seen absolutely loads of them across the UK, so we are very excited to see how many people report them and where," she added.
Participation in the Big Butterfly Count involves spending 15 minutes in an outdoor location, such as a garden or park, and recording any painted lady butterflies seen. The count runs until Sunday, August 9. Further details and participation instructions are available through the Big Butterfly Count app or its website, bigbutterflycount.org.